Control & Coordination in MAMMALS Flashcards
what is a hormone?
is a chemical substance produced by an endocrine gland and carried by the blood
What does a hormone (chemical) transmit?
- what does it alter?
They are chemicals which transmit information from one part of the organism to another and bring about a change
They alter the activity of one or more specific target organs
What are hormones used to control?
functions that do not need instant responses
What does the endocrine gland produce? What is it collectively known as?
The endocrine glands that produce hormones in animals are known collectively as the endocrine system
What is a gland?
is a group of cells that produces and releases one or more substances (a process known as secretion)
What type of hormones are released into the blood?
insulin, glucagon, ADH and adrenaline are cell-signalling molecules
Why do Endocrine glands have a good blood supply?
as when they make hormones they need to get them into the bloodstream (specifically the blood plasma) as soon as possible so they can travel around the body to the target organs to bring about a response
What type of cells do hormones only affect?
only affect cells with receptors that the hormone can bind to
- These are either found on the cell surface membrane, or inside cells
- Receptors have to be complementary to hormones for there to be an effect
What type of hormones are peptides or small proteins?
insulin, glucagon and ADH
insulin, glucagon and ADH
- They are water-soluble and so cannot cross the phospholipid bilayer of cell surface membrane
- These hormones bind to receptors on the cell surface membranes of their target cells, which activates second messengers to transfer the signal throughout the cytoplasm
What type of hormones are steroid hormones?
testosterone, oestrogen and progesterone
testosterone, oestrogen and progesterone
They are lipid-soluble and so can cross the phospholipid bilayer
These hormones bind to receptors in the cytoplasm or nucleus of their target cells
The human nervous system consists of the:
Central nervous system (CNS) – the brain and the spinal cord
Peripheral nervous system (PNS) – all of the nerves in the body
What does the Central nervous system (CNS) include?
the brain and the spinal cord
What does the Peripheral nervous system (PNS) include?
all of the nerves in the body
What does the nervous system allow us to make sense of?
our surroundings and respond to them and to coordinate and regulate body functions
How is info sent through the NS?
As nerve impulses
What is a nerve impulse?
electrical signals that pass along nerve cells known as neurones
What is a nerve impulse?
electrical signals that pass along nerve cells known as neurones
What is a nerve cell known as?
Neurone
What is a bundle of neurones known as ?
nerve
What do neurones coordinate?
print out the table
the activities of sensory receptors (eg. those in the eye), decision-making centres in the central nervous system, and effectors such as muscles and glands
Neurones have a long fibre. What is it known as?
An Axon
What is the axon insulated by?
by a fatty sheath with small uninsulated sections along its length (called nodes of Ranvier)
what is the axons sheath made of ?
myelin, a substance made by specialised cells known as Schwann cells
On the axon their cell bodies contain many extensions called?
dendrites
This means they can connect to many other neurones and receive impulses from them, forming a network for easy communication
When is Myelin made?
What does this mean?
when Schwann cells wrap themselves around the axon along its length
This means that the electrical impulse does not travel down the whole axon, but jumps from one node to the next
This means that less time is wasted transferring the impulse from one cell to another
What are the 3 main types of neurones?
sensory, relay and motor
Sensory neurones
carry impulses from receptors to the CNS (brain or spinal cord)
Relay (intermediate) neurones
are found entirely within the CNS and connect sensory and motor neurones
Motor neurones
carry impulses from the CNS to effectors (muscles or glands)
Motor neurones have:
A large cell body at one end, that lies within the spinal cord or brain
A nucleus that is always in its cell body
Many highly-branched dendrites that extend from the cell body, providing a large surface area for the axon terminals of other neurones
Sensory neurones have the same basic structure as motor neurones, but have
A cell body that branches off in the middle of the cell - it may be near the source of stimuli or in a swelling of a spinal nerve known as a ganglion
What do Sensory neurones, relay (intermediate)?
neurones and motor neurones work together to bring about a response to a stimulus
What is a reflex arc?
a pathway along which impulses are transmitted from a receptor to an effector without involving ‘conscious’ regions of the brain
What does the reflec arc not involve?
the brain
As a reflex arc does not involve the brain, a reflex response is..
quicker than any other type of nervous response
Examples of simple reflex actions that are coordinated by these pathways are:
Removing the hand rapidly from a sharp or hot object
Blinking
Focusing of the eye on an object
Controlling how much light enters the eye
In the example above:
A pin (the stimulus) is detected by a pain receptor in the skin
The sensory neurone sends electrical impulses to the spinal cord (the coordinator)
Electrical impulses are passed on to relay neurone in the spinal cord
The relay neurone connects to the motor neurone and passes the impulses on
The motor neurone carries the impulses to the muscle in the leg (the effector)
The impulses cause the muscle to contract and pull the leg up and away from the sharp object (the response)
define receptor cell
A cell that responds to a stimulus
What are receptors?
transducers
define transducers
they convert energy in one form (such as light, heat or sount) into energy in an electrical impulse within a sensory neurone
Where are receptor cells often found?
in sense organs (eg. light receptor cells are found in the eye)
Why are some receptors specialised cells?
for eg:
- light recpetors in the eye and chemoreceptors in taste buds
- they delect a specific types of stimulis and influence the electrical activity of a sensory neurone
Other receptors, such as some kinds of touch receptors, are just the ends of the sensory neurones themselves